PM Update: Hazy, toasty and humid for the Fourth, but storm risks minimal
Listen 3 min Comment on this story Comment Gift Article Share
* Code Orange air quality alert Tuesday for fine particulates from firework smoke * 9:50 p.m. update: The storm threat isn’t quite over yet for the D.C. area this evening. Areas of heavy rain and lightning in southeast Loudoun County and portions of central to northern Montgomery County are tracking to the east. If they don’t fizzle out, they could move into and through northern Prince William, Fairfax, southern Montgomery, and Howard counties during the next 45 minutes or so, and then through the Beltway and District after about 10:30 p.m.
Our forecast in detail...
We notched our second day in a row at 90 degrees or higher, which means we may be on our way to our first heat wave of the season — typically defined as at least three days in a row of 90s. The humidity is painful, with dew points in the low and mid-70s again today, but we’re actually running a good deal behind on 90-degree days so far, now at six or about half normal. Concerns for Independence Day are few. Heat, humidity and haze are the main ones. Smoke is a common issue with fireworks, and it has prompted the air quality alert for D.C. and northern Virginia counties tomorrow.
Advertisement
Through tonight: With the severe weather threat waning, a storm or two can’t be totally ruled out. Any can be locally strong through the evening. Skies turn clearer with time as winds shift to the west then northwest or north by morning. Some patchy fog is possible in places it rained a good deal, as lows settle to a range of near 70 to mid-70s.
View the current weather at The Washington Post.
Tomorrow (Independence Day): Pretty typical for the Fourth of July around here. Partly sunny, muggy, hot and increasingly hazy. A light north wind behind today’s cold front means somewhat drier air, but barely so. Dew points are still deep into the 60s as temperatures rise to around or above 90, which puts heat indexes in the mid- and upper 90s during the afternoon.
Advertisement
An isolated thunderstorm isn’t impossible, but odds are better south and east of here, and mainly during the afternoon. By fireworks time, worry about rain should be quite minimal. Light winds out of the north may even help with the view in the city.
See Jason Samenow’s forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter and Instagram. For related traffic news, check out Gridlock.
A smoky July Fourth: As noted during the smoke outbreaks in June, Code Orange or Code Red fine particulate pollution is often a Fourth of July kind of thing and rarely otherwise. It’s the reason for the Code Orange tomorrow, while the following days are expected to reach Code Orange because of ozone, which is more typical for midsummer.
The image below highlights the effect, which was at an extreme in 2019 due to an atmospheric condition called an inversion — warmer air above cooler air at the surface — trapping fireworks smoke. While the impact is most noticeable following the major shows, air quality tends to diminish through the day and into the night, with plenty of individual fireworks displays throughout.
Want our 5 a.m. forecast delivered to your email inbox? Subscribe here.
Gift this article Gift Article
Source: The Washington Post
